The research will explore a method to develop realistic estimates of the use of drugs and assure prescribing quality in an HMO by comparing observed prescribing rates with expected prescribing rates. Expected prescribing rates will be based on knowledge of problems (morbidity and preventive needs) encountered in the enrolled population. An abstract theoretical model and an applied model institutionalizing the method will be formulated. The applied model includes HMO physicians and expert participation in selecting a problem for which a therapy protocol is desired and in producing the protocol. Medicine use for one problem will be tested under the method for prescribing quality among physicians and physician assistants both before and after protocol formulation. The methods will be tested in two HMO sites, one of which will participate in protocol development. Another site will have no input but will simply be provided the protocol. A third site will be used as a control condition in which the protocols will not be implemented. An assessment of whether observed use deviates from expected use will be made in each site for each prescriber before and after protocol implementation, thus indicating what effect a protocol has on prescribing, and whether active participation in protocol formulation makes a difference in prescribing patterns. A cost efficiency estimate for method application will be made and a method to modify physician prescribing behavior will be suggested. The research will explore the limitations of the method and its applicability to larger providers or reimbursers of care.